cgroupns: Add a limit on the number of cgroup namespaces

Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 984f73b..1ed9281 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -621,6 +621,7 @@
 	atomic_t		count;
 	struct ns_common	ns;
 	struct user_namespace	*user_ns;
+	struct ucounts		*ucounts;
 	struct css_set          *root_cset;
 };